1. Field of the Invention
This invention is directed to an apparatus for assisting persons to breathe in hostile environments. It more particularly relates to such an apparatus that is useful in purifying contaminated air as well as providing portable clean air.
2. Background of the Prior Art
There are, at present two systems for assisting the breathing of persons who are subject to contaminated air. First, there are the supplied air systems, such as Self Contained Breathing Apparatus (SCBA) that feed compressed air (e.g. bottled) to a tight fitting facemask, or other conduit to the mouth and/or nose, for inhaling by a user. These systems do not permit the user access to the ambient atmosphere at all. Second, there are filter/decontamination systems for use in the form of a canister, in connection with a respirator apparatus that rely on cleaning ambient atmosphere to make it suitable for breathing. Such filter systems may or may not make use of auxiliary power. In powered systems, ambient atmosphere is sucked through a suitable filter/decontamination means, or other purifying means, by a powered fan or the like, such that the contaminated ambient air is rendered breathable. The purified resultant air is fed to a headpiece of some kind, such as a tight fitting facemask. The complete system is known as a Powered Air Purifying Respirator (PAPR). Both types of breathing assists are used by personnel who are subject to breathing ambient atmosphere that would otherwise be considered to be harmfully contaminated, un-breathable, or dangerous air.
A dangerous or un-breathable atmosphere is considered to be air containing less than 19.5 volume percent oxygen, or air with the requisite oxygen, but also containing significant proportions of harmful contaminants, e.g. particulate or gaseous. It will be appreciated that, in some situations, (where the oxygen content is at least 19.5%), a wearer may be able to enter an area that has a contaminated atmosphere using only a filter system, provided the filter(s) is capable of meeting the challenge of the contamination, as a result cleaning the atmosphere and enabling the user to breath and still preserve his health. The filter can be provided with means to eliminate harmful constituents in the wearer's ambient atmosphere. In particular, filter based decontamination systems, that is, those systems that purify an ambient atmosphere that has become contaminated so as to convert it to breathable air, work best when they pass an air supply under positive pressure through a cleaning element (such as a suitable filter). That is, a pump/fan is used to suck the contaminated atmosphere through a filter, and perhaps into contact with a material that ameliorates the contaminant(s), and to then force the purified, e.g. filtered, air under positive pressure into a facemask or other means associated with the breathing of the wearer, such as a mouth grip, hood, or helmet. While a powered air supplying means, such as a battery operated pump/fan, is probably preferred, it is also known that air cleaning systems that are not powered by external means can be used. In these unpowered systems, the user's lung power provides the necessary impetus to force contaminated air through the cleaning element and feed it to the user. For simplicity, this means of cleaning ambient atmosphere will be referred to as an Air Purifying Respirator (APR). When the air is forced through the system due to the use of a battery, line current or other powered pump or fan arrangement, the operating system is known as a Powered Air Purifying Respirator (PAPR).
A powered air purifying respirator system (PAPR) will protect against contaminants so long as the oxygen level in the purified air is above 19.5 volume percent and provided the contaminants are such as can be removed by filtration, e.g. soot and smoke, and/or can be ameliorated by reaction with a suitable purifying material. In practical effect, these systems have been designed to use replaceable filter(s) and air purifying canister(s). However, they are of no value where the ambient atmosphere has an oxygen content that is less than 19.5% by volume.
Other situations exist, such as where the ambient atmosphere is so contaminated, or the contamination is such, that a filter and/or decontamination/purifier system cannot handle the problem; and/or the oxygen content of the ambient air is too low to satisfy human survival needs (that is, where the atmosphere is IDLH, that means the ambient atmosphere is of Immediate Danger to Life and Health). In those circumstances, a person entering the area with such level and type of contamination must take his own air supply along with him. This is akin to a SCUBA diver carrying his air with him in the form of a container (bottle) with compressed, clean air in it.
One problem is that a wearer of a SCBA must support all of the weight of the bottled air whereas, in water, a diver has the advantage of the water's buoyancy to help support the weight of the SCUBA tanks. Even so, most SCBA systems are only capable of carrying enough bottled, compressed air for up to about an hour's use. It would, of course, be most desirable to be able to increase the time that a user, for example a fire fighter, can work in a hostile environment dependent upon bottled air while at the same time minimizing the weight that the person must carry to support him for that additional time.
It will be appreciated that air bottles are heavy, especially when they are full. In the case of fire fighters, they are already going into an unfriendly environment carrying their tools with them, and the heat of the fire makes it even more difficult to carry the extra weight of the compressed air container. Further, the fire fighter must often proceed, from the safe ambient air outside the area where a fire has merely contaminated the atmosphere to an extent such that it can be cleaned, by wearing some form of APR, for a relatively long distance before he reaches an area where the contamination is of such an extent that the atmosphere cannot be reasonably cleaned and where he must breath the air he brought with him, or strangle from lack of oxygen, or be harmed by other contaminants.
When carrying around ones' own air supply, there is a very real practical limit as to how much air can be safely carried. Contrary to operating under water with a SCUBA rig, the air bottles used by fire fighters are quite heavy, must be supported entirely by the wearer, and do not have the advantage of water buoyancy partially supporting their weight. Making them larger, to be able to carry more air, increases their weight but decreases their portability. This combination of weight and working conditions severely limits the time that a fire fighter, who is wearing/carrying his own air supply and tools, can effectively fight the fire.
Thus, there exists a situation in which a fire fighter, for example, does not need carried air for some portion of the time that he is working on the fire, but does need portable, bottled air for other portions of the time that he is working on the fire. Yet, existing systems are suited to one or the other; that is, the existing systems either provide positive pressure (pumped) filtering and purification systems to convert contaminated ambient atmosphere to air that is clean enough to breath safely, or they provide bottled air under pressure that is carried by the person to be used instead of the ambient atmosphere. While both systems have deficiencies, each system has advantages, even necessities, under critical conditions.
The above and following comments use a fire fighter as illustrative of the type of person who will benefit from using the instant invention. However, this invention is by no means limited in use to fire fighters. Workers in chemical plants and refineries will have substantial need for the benefits available from the instant invented system. Soldiers in the field that are being subjected to chemical or biological attack will benefit greatly from the instant system. It will be apparent to those of ordinary skill in this art that others will similarly be assisted by the instant invention